In the field of irrigation where repetitive, periodical, timed operation of a water supply system is required there has been a need for an inexpensive, extremely reliable, easily programmable timing and control system. The irrigation system can be used for as varied applications as the repetitive humidification spraying of plants in botanical gardens and hothouses to the supplying of water to large golf courses where the particular amount of water required at particular locations differs depending upon the location.
Of those control systems which are currently in use in the field, almost all of them rely on a mechanical timer. Although the mechanical timers have become quite sophisticated and can provide a plurality of different time sequences in a sequential, predetermined manner, the devices still require the operation of a mechanical, moving switch means. Such switch means are prone to frequent failure as the switch contacts get dirty and worn.
It is also known to use a digital computer operated control system in which a general purpose, digital computer controls the timing functions. Unfortunately, such systems are extremely costly, quite bulky, difficult to maintain, and difficult to program by an operator who has not had extensive training. Furthermore, because of the temperature and humidity conditions in the field, such systems have not been completely reliable. Finally, upon the loss of power, these computer controlled systems lose all their preprogrammed RAM memory and the entire system must be started up from scratch. Naturally, this requires skilled personnel to reprogram the computer with the attendant increased maintenance costs of the system.